1. Field of the Invention
The invention relates to a rock drill having radial recessed grooves for locating cutting bodies therein which are to be brazed in, and in particular to a rock drill for break-throughs having a drill head body which is arranged at the end of a drill shank and has at least two radially projecting lobes provided with cutting bodies and also has a central extension which has cutting bodies and is axially arranged in the drilling direction in front of the lobes.
2. Background of the Art
In known rock drills, carbide cutting bodies are brazed by the brazing method into cutting body locating grooves of a steel drill head. At the same time, the depth of the cutting body locating groove is of such a size that the cutting body sits on the groove route during the brazing process in order to achieve a precisely defined position. With this method, it is accepted that, during the brazing process and as a result of the considerably different coefficients of expansion of carbide and steel (factor about 1:2), stresses will develop particularly in the lower area of the recessed groove which can lead to weakening of the connection during extreme loading.
This problem is equally known with normal rock drills as well as with rock drills for producing break-throughs, such as can be inferred, for example, from German Pat. No. 2,414,354. The center extension on such tools is principally constructed in the same way as normal carbide drills; that is, the center extension has an appropriate carbide cutting body. In addition, it is also necessary with the known rock drills for making break-throughs to incorporate grooves or holes in the lobes pointing radially outwards, which grooves or holes are used to locate the carbide cutting bodies in the lobes. These individually tip-locating grooves in the lobes must be made by means of end milling cutters or similar, which makes the manufacturing process more expensive.